A location detecting apparatus which acquires location information of a mobile object is applied to various mobile objects. When the location detecting apparatus is applied to a vehicle, an on-vehicle device mounted on the vehicle is responsible for acquiring location information of a mobile object.
In a next generation road pricing system, a flexible pricing system based on a travel distance, a time period while a vehicle stays within a specific area, or the like, is desired. To achieve this, it is necessary to detect correct location information of each vehicle. As means for detecting a location of a vehicle, a GPS (Global Positioning System) is mainly used as a feature of the on-vehicle device. This is a method which utilizes GPS trajectory information according to a GPS radio wave signal from a GPS satellite. It takes some time to perform communication with the GPS satellite to establish the GPS trajectory information. Particularly, it takes much time to detect location information for the first time after power activation. Therefore, it is desirable to shorten a time period required for acquiring the GPS trajectory information.
A time period required for outputting location information for the first time from power activation of the on-vehicle device is referred to as initial location calculation time. For example, if the vehicle starts moving before the initial location calculation time has elapsed after power activation, a route cannot be correctly obtained, and accounting cannot be performed correctly.
Therefore, as a method for shortening a time period required for acquiring the GPS trajectory information, in Patent Citation 1, broadcast stations for wireless LAN are provided at numerous locations, and information from the GPS satellite is transmitted to each vehicle via a wireless LAN broadcast station. Patent Citation 1 discloses a method of eventually enabling acquisition of the GPS trajectory information using exchange of high-speed communication.
Patent Citation 1: Japanese Unexamined Patent Application, Publication No. 2005-69767